SPEEDING-UP REPAIRS AND REPLACEMENTS.
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A Method of Expediting Workshop Operations by the Use of an Appliance Which Lifts a Vehicle Well Clear of Ground Level.
ANY engineering establishment in which the maintenance of motor vehicle fleets. is attended to and overhaul and repair work undertaken, is usually provided with one or more inspection pits sunk into the floor, over which a vehicle can be -run when it is desired to inspect or 'carry out work Upon the under gear. It is certainly possible by these means • to make replacements and effect necessary adjustments, but such pits undoubtedly possess
several drawbacks. •
If the pit be but a shallow one, the mechanic is cramped at his job and his movements thus impeded, whilst invariably he has to work by the aid of an inspection lamp. Moreover, with the ordinary form of garage-pit, supervision of the task in hand is at all times difficult, and therefore the workman has to shoulder a greater responsibility. Then, again,there is the difficulty of keeping the pit clean and of avoiding the accumulation of waste oil and grease which does not always find its way into drainage troughs.
It was a realisation of these disadvantages that impelled Alister Kirk and Co., Ltd., traction engineers, of Ballarat Street, Belfast, to devise a better method of inspection than that provided by the averav pit. It was a matter of roach concern to them, for, undertaking maintenance and repair work on a large scale, it was necessary to execute work with the utmost expedition, and thus get their clients! vehicles back on to the road with the least possible delay. It -should be mentioned at—this juncture that the company are agents for Leyland Motors, Ltd., and that a large number of their customers is made up of owners of single vehicles. Thus, it will be seen that it was imperative for them to provide tideQuate service facilities.
In approaching the problem from various angles, first thought was given to . the possibility of arranging an overhead structure with a platform: above floorlevel, which may be reached by way of an acutely inclined ramp. The disadvantages of such a scheme were self evident, so the company turned their attention t o the question of elevating through the medium of hydraulic-power.
A number of experiments in this direction served to
prove the practicability of the idea, but its application was deemed too expensive to proceed with, largely due to the necessity for using distributor gear in order to obtain a perfectly even lifting movement on, say, four rams, owing to the variation in axle weights.
After further probing of ways and means of solving the problem, it was finally decided that the only practical method was to elevate a vehicle from floor-level by means of four tall jacks coupled by shafts and bevel gearing operated by an electric motor with a reversing controller of the tramway pattern.
An elevator was accordingly built on these lines, and since its installation it has proved indispensable. Our two
photographic illustrations serve to indicate the design and application .of the elevator, whilst the line drawing shows its general layout and the method of Operation. _ We would particularly draw attention to the fact that the 'screws are housed in tithes partly filled with oil, which. serves to lubricate the threads throughout their entire length, and thereby re.dace friction and, consequently; wear.
The plan view clearly shows the disposition of the electric motor and the method of conveying the drive to" the transverse shafts. The maximum lift of the screws—i.e., from the top of the phosphor-bronze nuts in which they bear —is 5 ft. 6 ins., a like tlimension separating the centre points of the channel platforms on which the vehicle -i5 supported. The space between the inner flanges of these platforms is filled in by stout floorboards, carried on brick or concrete ramps. 'The bed for the electric motor is outside the limits of the elevator proper, and is provided with a separate inspection cover.
It is obvious that to carry the weights likely to be imposed upon an elevator of this description it must be solidly built, particularly when it is borne in mind that the distance between the screws iii the longitudinal direction is 15 ft. There is a foundation of concrete below each of the four pedestal bases, which, it should be stated, have brass liners.
To substantiate the claims of efficiency made for the Kirk elevator, we can refer to a test which the company carried out some months ago in the presence of tw3 well-known consulting engineers. On this occasion a lorry weighing, with Its load, 10 tons 19 cwt. 2 qrs., was driven on to the elevator, and an ammeter, which was connected with the
motor circuit, showed a momentary reading on starting under the load of 35 amps., which dropped to 24 amps. throughout the period of elevating. We are informed that there was no appear once of stationary friction when startlug under load.
The screws were then. lowered and a further test made to ascertain the rapidity with which they could be raised from ground level. It was found that 1 ft. was reached in 25i secs., 2 ft. in 500 secs., 3 ft. in 75-4 sees., and 4 ft. in 100 sacs. A calculation showed an allround efficiency of 50 per cent. on the four screws. The motor used in conYnnetion with the hoist in this test had a capacity of 220 volts. From the performance of the elevator in this series of trials the opinion was expressed that such an appliance was capable of elevating much heavier loads than that dealt with in this particular demonstration.
The manner in which an elevator of this type has enabled Alister Kirk and Co., Ltd., to speed up their repair work can be gauged by referring to the sequence of operations undertaken when a lorry engine has-to be overhauled. The vehicle is first drivetr on to the elevator, and, after it is raised, men working below the chassis disconnect clutch couplings, remove undershields, and drain the radiator, while others sever the waterpipe joints and prepare the unit for lifting:
In the meantime, another engine has been taken from stock—the company carry spare units such as engines, gear-. boxes and back axle—arid lifted by a heavy-duty mobile crate (it is to be seen in one of our pictures) ready for lowering into position in the chassis. The whole operation can be effected in 3 hrs. 20 mini., and the company are confident
that, with an improved organization, they will ultimately' be able to effect such a task in about 2i/hrs., largely as a Jesuit of the use of up-to-date equip
meat as exenapiified by the Kirk elevator.
To the owner of si single vehicle the time factor is of paramount importance,